Why did researchers originally think that protein was the genetic material?

Answer 1

Researchers originally thought that protein was the genetic material because proteins had specific functions with great heterogeneity. Enzyme holds DNA strands apart because of a single stranded binding protein.

Answer 2

Even after DNA was discovered people thought that proteins were the genetic material, so it had little to do with the order of discovery. It boils down to variety: it was known that proteins were made from 20 different amino acids, while DNA is made of only four different bases. It kinda makes sense, then, that proteins could code for MUCH greater variety in their amino acid sequence than DNA could in its nucleotide sequence.

Keep in mind also that DNA replication, transcription, and translation were not known at this point. People knew what DNA was, but not what it could do.

The first solid evidence that it was DNA (and not protein) that confered heritable traits from generation to generation came when some very clever researchers laced one set of bacteria-invading viruses with radioactive sulfur, and another set with radioactive phosphorus. Viruses contain both proteins and nucleic acids, and it was known that viruses injected their genetic material into bacteria, whatever that genetic material might be. Since sulfur is found in proteins, but not nucleic acids, and phosphorus is found in nucleic adids, but not in proteins, it stood to reason that whichever radioisotope showed up inside the infected cells would betray the genetic material.

As it turns out, the viruses that carried radioactive sulfur didn't transfer that sulfur into their host cells, but radiophosphorus DID appear inside the cells infected by the other set of viruses. The conclusion was obvious: the viruses injected nucleic acids, and not proteins, into the cell when they hijacked the cell's genetic machinery.

As the experimental evidence mounted, the idea that proteins were the genetic material passed out of favor.

I know that's more than what you asked, but maybe it will help you in some way. Good luck!

Answer 3

Before the 1950's scientists believed that protein was the genetic material of the cell. Hope that helps.

Answer 4

most likely RNA

Answer 5

RNA

Answer 6

Proteins